Regadenoson (2-{4-[(methylamino)carbonyl]-1H-pyrazol-1-yl}adenosine) is an A2A adenosine receptor agonist and is indicated for radionuclide myocardial perfusion imaging (MPI) in patients unable to undergo adequate exercise stress. It was approved by the United States Food and Drug Administration in 2008, marketed under the trade name Lexiscan.
U.S. Pat. Nos. 6,403,567, 7,732,595 and U.S. Publication No. 20110144320 described a series of processes for the preparation of 2-Adenosine N-pyrazole compounds, including regadenoson. However, the processes comprise reacting genotoxic hydrazine with 2-iodoadenosine for the preparation of intermediate 2-hydrazinoadenosine which is also a potential genotoxin. The hydrazine-related impurities deemed as genotoxic impurity (GTI) or potential genotoxic impurity (PGI) would significantly affect the quality of final regadenoson.
U.S. Pat. No. 6,514,949 and WO 2012/149196 described processes for preparing regadenoson using 2-haloadenosine without hydroxyl protecting groups. The process resulted in low yield due to the formation of dimeric impurities having the formulae DI and DII:

Moreover, WO2012/149196 utilized the catalyst IDAAR-Cu2+ (iminodiacetic acid resin-copper(II)), which can be difficult to remove, resulting in metal contamination in the final regadenoson.
There remains a need in the art for a simple and safe process for industrial preparation of regadenoson. Surprisingly, the present invention addresses this need.